1. Field of the Invention
This invention relates to a heat transfer tube which is arranged to have improved performance when immersed in high temperature vapor to condense the vapor on a low temperature heat transfer face and also to a method for manufacturing the heat transfer tube.
2. Description of the Prior Art
Heretofore smooth tubes or low fin tubes have been used as heat transfer tube for condensers of refrigerators. Generally, in the initial stage of condensation, vapor condenses on a heat transfer face in a dewdrop-like state. However, the dropwise condensation becomes so-called film condensation as the condensation further proceeds until the heat transfer face is covered with a thick liquid film, which has a great thermal resistance to decrease heat transfer performance. This is a reason for poor heat transfer performance of the smooth tubes.
The low fin tube is provided with many fins which prevent the formation of a thick liquid film and increase the surface area of the tube for enhancement of heat transferring performance. Such advantageous effects attainable by the use of a low fin tube, however, has not been sufficient. In an attempt to further improve the heat transfer performance, there have been proposed new techniques. However, the new techniques proposed have not been satisfactory in economic aspect or in terms of easiness of handling of them.
In order to enhance the heat transfer performance during condensation, however, the surface of the heat transfer tube must be arranged to prevent the formation of a thick liquid film thereon and to readily remove condensed liquid therefrom as well as to increase the surface area of the heat transfer face.